package com.twu.biblioteca;

public class NullController implements Controller {

    private static final class InstanceHolder {
        private static final NullController INSTANCE = new NullController();
    }

    public static NullController getInstance() {
        return InstanceHolder.INSTANCE;
    }

    private NullController() {
        // hide constructor
    }

    @Override
    public void enter() {
    }

    @Override
    public Controller handle(String input) {
        throw new IllegalStateException();
    }
}
